Walking Fish Are Another Step Toward Evolution

Imagine a salamander speeding away from you as you walk around your favorite part of campus. Now exchange the legs for fins and the body for a fish body. Now imagine your salamander-now-fish in a cave.

Researchers from the New Jersey Institute of Technology have discovered a blind cavefish in Thailand that walks. While these fish don’t just get up and walk on their tails whenever they feel like it, they instead walk and climb walls in a way that’s similar to salamanders.

The Cryptotora thamicola is a blind fish that walks similar to the way land vertebrae do. Instead of moving themselves with one fin in front of the other, like some land animals, they move their pelvis left to right. It’s not dissimilar to an axis.

This is especially helpful when trying to make its way upstream on land.

“I was completely blown away,” researcher and Assistant Professor of Biological Sciences at New Jersey Institute of Technology Brooke E. Flammang said upon learning about these fish. “These guys seemed to be very leisurely walking up the rock face.”

“I’ve known about other species of fish that could walk, so this didn’t come as much of a surprise to me,” second-year environmental studies major Derek Cheung said. “I think this discovery is a great opportunity to look at how animals have adapted and evolved over time in response to their environment. What will these fish look like in the future when they learn to adapt even better to their surroundings?”

Although these fish aren’t the first to walk, they are the first to walk with an evolved skeletal structure. This is what makes these blind cavefish so different and interesting. Studying these fish provides more insight into the evolution of tetrapods.

“The discovery of this capability, not seen in any other living fishes, also has implications for understanding how the anatomy that all species need to walk on land evolved after the transition from finned to limbed appendages in the Devonian period, which began some 420 million years ago,” a press release by the New Jersey Institute of Technology said.

Because these fish are so unique, the species is actually protected. Researchers can’t take any of the fish back to the their labs to study.

Normally, the pelvic bone in fish is mostly used to help stabilize the pelvic fins. In fact, the pelvis is made up of a few small bones and not really considered a pelvic bone. Pelvic bones, a feature only found in mammals and amphibians, help join limbs to the spine.

In the cavefish, the pelvis is more complex, with a matrix of bones that fuse to the spine, similar to tetrapods. It allows the fish to move by supporting themselves on different pressure points instead of flopping around on their bellies to move. This movement resembles the walking of land animals.

“From an evolutionary perspective, this is a huge finding,” Flammang said. “This is one of the first fish that we have as a living species that acts in a way that we think they must have acted when they evolved from a fluid environment to a terrestrial environment.”